Did you ever look at a cherry tree and see the little black marshmallow-like swellings on the branches? Are there so many knots on the tree that they look like Christmas decorations? Are the neighbours hinting strongly with a pair of loppers in their hand that something should be done to your ‘diseased’ tree? If so, then don’t get out the chainsaw just yet…Here are some tips you can try.

Black knot fungus is an airborne disease most active in spring. In the winter when the trees are dormant is the best time to see the swollen growths. The dormant season also happens to be the best time to prune your trees as most diseases are inactive and you can really see the structure of the tree. If you are reading this article in Spring, wait until July until the bark has hardened and then perform an all-out pruning attack on your tree.

Black knot is an airborne fungus that only affects trees in the cherry family: Maydays, Schubert Chokecherries, Sour Cherry, and sometimes Amur Cherry can be infected with this fungus. The infections start out as swollen branches at the beginning of the year. By the end of the summer the knots look like black ‘poop on a stick’.

When pruning the tree, you may create a wound that will do more harm than good (a pruning class or expert advice is advised). Black knot on the tips of the branches is relatively easy to remove. Prune at least one foot below the point of infection. If the black knot gets into the trunk of the tree, the fungus must be carved out carefully to avoid harming the tree. Once the infection gets out of control in a tree, the only option left is to take the tree out.

A cherry tree should be pruned every two to three years. If a tree gets neglected, the many crossing and rubbing branches will create wounds. These wounds will be an entry point for disease. If you have had black knot pruned out of your tree, make sure you are watching it closely as the black knot may return.

Getting rid of black knot infected branches is best done by burying it in the landfill. Try not to burn black knot as this has been found to release the spores into the air; thus spreading it further. If you have access to a tree chipper, it will chip the branches and knots into tiny pieces; if the pile of wood-chips can heat up and compost for awhile, it will kill the spores and the wood-chips will be good to use.

Let’s take an active approach to removing black knot in our area. Many people will be planting cherries in the city because of the flowers and fruit they produce. Let’s keep the black knot at a minimum so we can enjoy the cherry trees for years to come.

BLACK KNOT FUNGUS…DON’T GIVE UP THE FIGHT.

(By: Robin Adair, Arbour Crest Tree Services Ltd.

Date: April 25, 2008 For: U of S Master Gardener Newsletter)

As an arborist who has spent most of his horticultural life in Calgary I was excited to move back home to Saskatoon. I wanted to see what sort of differences existed between the two climates. The most shocking thing I have seen thus far is the amount of black knot fungus around this City. There seems to be black knot (Apiosporina morbosa) on at least 60-70% of the cherry trees I’ve seen in and around Saskatoon.

The problem with black knot in Saskatoon and surrounding areas is that it is an airborne fungus that emanates from the native chokecherry stands along the river. Since the river extends right through the heart of the city, the spores can spread to all areas of town quite easily and quickly. If you have black knot on your tree, take a proactive approach and cut the infections out. If you see black knot on your neighbour’s tree explain to them what it is and get them to prune it out or hire an arborist to do so. If you see black knot on a tree on city property, call the City Parks office and ask them to prune the tree.

Black knot is an airborne fungus that only affects trees in the cherry family. In our area, Maydays, Schubert chokecherries, sour cherry and sometimes Amur cherry are ornamental trees that can be infected with this fungus. The infections start out as swollen branches and a few months later they form into knots look like black marshmallows.

The dormant season, when the fungus is most visible, is the best time to prune out infected branches. Prune at least one foot below the point of infection. Make sure you have taken a pruning class or have some idea how to make these cuts or else the wound you create may do more harm than good. If the black knot is on the tips of the branches then this is relatively easy to remove, but if the black knot gets into the trunk you can only try to carve out the fungus carefully to avoid harming too much cambium of the tree. Once the infection gets out of control the only option left is to take the tree out.

A cherry tree (especially Mayday and Schuberts) should be pruned every two to three years. If a tree is neglected, the many crossing and rubbing branches will create wounds, and these wounds will be an entry point for disease. If you have pruned black knot out of your tree, make sure you are monitoring it closely for black knot in case it returns.

The best thing to do with infected cuttings is to bury them at the landfill. Burning the branches has been found to release the spores into the air. If you have access to a tree chipper it will chip the branches and knots into tiny pieces. When a pile of wood-chips is left to compost for awhile, the heat will kill the spores and the wood-chips will be good to use.

Let’s take an active approach to removing black knot in our area. A lot of people will be planting cherries around Saskatchewan because of the flowers and fruit produced. Let’s keep the black knot to a minimum so we can enjoy the cherry trees for years to come.

CONTROLLING TREE STRESS THROUGH PROPER TREE MANAGEMENT

(For Calgary Hort Society Calgary Gardening–July 2007)

‘As long as there is energy, the tree can fend off injury’. This is a phrase that I get my students to repeat back to me whenever I teach. What it means is that if you keep your tree healthy by proper pruning (see previous article), you will have a happier tree. This article will focus on the many aspects of tree care other than pruning that the homeowner can do to keep trees stress-free. You never know what Mother Nature will throw at us, but these ideas might help weather the storm.

A well planted tree will do best compared to others because its roots will be happily growing into nice soil. Many trees get planted too deep, thus burying the roots too far down to get adequate moisture and air. Sometimes we can do everything horticulturally possible to aid a tree but if it was not planted properly, it will be tough to fix. The tree will be in decline and looking stressed and no amount of arboricultural magic will help it survive. Along with the many tips an arbourist can give about proper planting, make sure your young tree has a proper stakeon it so it does not fall over with our year-round strong winds. Also, make sure the tree is planted in the right spot. It can’t pull up its roots and leave (pun intended). Once a tree has its roots set in the ground that’s where it stays all its life.

Tree fertilizing is one example of tree management. In Calgary, professional arbourist companies will provide this service usually twice a year. Think of this as giving vitamins to your tree to keep its immune system up. When choosing fertilizer, make sure that you have the right amount of Nitrogen, Phosphorous and Potassium (N-P-K) in the mix at the right time of year. Use higher N values in the spring for green-up and higher P values in the fall for root growth. Interestingly, Calgary soil has been found to be low in N due to the high amount of rainfall the past two Junes. However, don’t try to give too much fertilizer at once. This is a treatment that will take a year or so to produce results.

Drinking more water, a health tip often discussed in the media for human health, is also a most essential part of a tree’s healthy development. Make sure the tree has water at the right times of year but do not over-water. Check that the soil is not saturated a day or two after watering. Snow-farm in the winter by putting snow at the base of your trees and around your foundation plantings will help insulate and hydrate the soil during Chinook conditions. Placing a downspout or a weeping tile system from your eavestrough to the base of your tree, will help keep water away from the house and pointed to where the tree needs it.

Use mechanical barriers to prevent injury which will stress young trees. One of the worst killers of trees in urban settings is ‘weed-wacker blight’. Every time the bark of a tree is weed-wacked, it girdles the tree so it can’t move nutrients up and down through its vascular system. The biggest threat to new trees in my neighborhood is rabbits. If they end up chewing more than half of the bark around the base of the tree, the tree will die. To prevent this damage, try using perforated weeping tile, cardboard, chicken wire (or all of the above) around the base of the tree, until the tree gets old enough to have stronger bark.

Another important tree management technique is the use of wood-chip mulch. 3-5 inches of good wood –chip mulch will have many benefits to your tree. In the forest, trees do not have grass growing at their base but thrive on wood-debris, compost and natural nutrient recycling. Mulching with wood-chips has been around for a long time but is getting more popular as there is a need for water conservation.

Through these techniques, the tree will have a better chance of competing in our tough climate. As with human health, our trees should be kept stress-free in order to stay ahead of the next emergency and be better off in the long-run.

Pruning trees every 2-3 years produces tangible rewards that keep a good arbourist going. Although I don’t consider myself a ‘tree hugger’, I have talked many people out of cutting down trees. Some people worry that if the tree is leaning or if the tree is too big then it will fall. It is rare that a tree will fall over unless the roots have been disturbed. Especially in Calgary, it is better to try to prune the tree than to cut it down. When caring for a tree, make sure to keep the tree as stress- free as possible so it can withstand most of what Mother Nature has to offer.

Looking back at pruning I have done over the years, I can see a change in philosophy towards less is more. Most people think that pruning involves removal of complete branches. The most obvious example of this would be with spruce trees that are limbed up. When a spruce bough is cut off it will never re-grow to the length of the other branches. As long as you leave green needles on a spruce branch it will stay alive. Professional arbourists would recommend simply shortening the lower boughs back in order to give enough clearance from sidewalks, driveways and for mowing.

For deciduous trees, the shortening back method is often better than complete branch removal. Instead of cutting that limb over the neighbor’s roof completely off, just shorten it to an upright leader. You may end up taking off 1/4 to 1/3 of the length of the limb so that the tree doesn’t have to be stressed about fixing a big wound back at its trunk. If you make a cut that is too big, it will cut into the heartwood of the tree and the tree will not be able to seal that wound.

Another misconception regarding pruning is that the tree must be brought down in size. Arbourists use crown reduction techniques and shaping techniques to keep trees low headed for view, fruit production, utility line-clearance and Japanese style pruning. Most every day pruning involves leaving the tree tall. Removing deadwood, damaged and diseased branches is the basic 3-D’s we all first learn when pruning. Crossing and rubbing branches can be removed as well as shortening branches to reduce width. These pruning methods usually are sufficient for 2-3 seasons. Be careful not to remove too much inner growth when pruning your tree, also known as lion’s-tailing. This usually happens when a lazy arbourist does not get up to the top or out to the ends of the branches when pruning.

Keep your trees disease free. There is nothing more stressful to a tree than disease. You need to know the types of diseases out there and how they can be controlled. The worst (and most evident) tree disease in Calgary is black knot fungus which only affects certain trees in the cherry family. Make sure to cut out the black knot as soon as you see it to avoid its spread. Fireblight, a bacterial disease that only affects the apple family, is an overly diagnosed disease. Be very careful in cutting this stuff out. Cut well below the point of infection and keep your tools clean.

You can always prune more next year. Various studies done in the past 10-20 years come to the same conclusion…less is more. The rule of thumb used to be, you can only prune off up to 1/3 of the live material in a tree per growing year. Now we recommend taking only up to ¼ of the live material per season. For older trees only take off 1/5 of the live material. For stressed or struggling trees do not take off any live material at all. This is especially true in Calgary where we have such tough growing conditions.

Some people are timid about making those first cuts on their trees. Some people are too over-eager and take too much off their trees. Take a course before you prune in order to feel confident and safe in your pruning methods. Sign up for a tree care course in order to protect your investment in your landscape and be the envy of all your neighbors.

PROPER CUTS NIP DISEASE IN BUD

But wait.You’ve raked up the leaves and cut back the perennials. Now you’ve got your eye on taming a wild and woolly lilac bush that’s leaning way over into your neighbor’s yard.(Article Published in the Calgary Herald – Thursday, October 13, 2005)

Your neighbour advised you to prune in the summer after they flower. But didn’t your grandmother always say lilacs should be shaped in the dead of winter? If you don’t root out the truth before sharpening the shears, you could do more harm than good.

“Making improper cuts can lead to damage to the tree — sometimes irreparable,” says Robin Adair, owner of Adair Tree Care in Calgary and an instructor with the Calgary Zoo’s Master Gardener program.

“Tearing can encourage disease, and over-thinning can lead to stress. Some people think pruning is like giving the tree a haircut. You have to know what you’re doing or you’ll stress out your trees.”

Stressed trees become weak and prone to disease, while a stress free tree is able to stand up to whatever Mother Nature throws at it, like snowfalls in June.

Adair advises that fall pruning should start after a tree has lost its leaves, except for birch and maple trees, which should be pruned when they’re in full leaf. Trees that sucker, such as poplars, shouldn’t be removed during the cold months, because nutrients are stored in the roots, and if any are left behind, they’ll grow like crazy come spring.

By law, elms must be pruned in winter because of the risk of Dutch Elm Disease, even though there are few communities in our province that have been affected by it.

Fruit trees should be pruned in the winter because you can see the structure of them really well, says Adair, and there’s less chance for disease such as fireblight to set in.

An absolute no-no this time of year is pruning of lilacs and Nan King Cherry bushes.

“That’s one of the first lessons I ever learned as a kid,” says Adair. “You’ll be pruning off their flower buds. You should prune them after they flower.”

Trees and shrubs that can be pruned any time of year are evergreen trees, junipers on the ground and hedges such as cotoneaster.

“But if you use an electric trimmer, make sure it’s sharp,” he advises.

He also recommends home owners harden off their trees before the first big snowfall of the year. Watering should be held off from mid-September to mid-October, and then around Halloween, the whole area under the trees and shrubs should be drenched. This ensures the trees will have moisture in Calgary’s driest months, which are generally February through April.

Adair recommends Felco brand saws and hand pruners for their durability, and insists that amateurs should take a course on pruning to ensure the vigour of their trees and shrubs. Information on programs is available from the Calgary Zoo and the Calgary Horticultural Society.

As little as 3 years ago, I was recommending that homeowners plant Manchurian Ash Fraxinus mandshurica and Black Ash Fraxinus nigra. “They are hardy to this area” I would say, “These two trees have a nice shape and they don’t have many predators.” I have since changed my tune. With the arrival of the Cottony Ash Psyllid into Calgary’s urban forest in the last 2-3 years, 80-90% of the Black and Manchurian Ash trees that I have seen have been ravaged by this pest. One can only guess that with the drought that started at the turn of the century, this pest has overwintered well and can now be considered an infestation.

Signs & Symptoms

Also known as tree lice because of their white/cottony appearance, the Cottony Ash Psyllid injects a toxin into the leaf that curls the leaf and creates a little cocoon wherein the Psyllid hides from predators and tree-spraying equipment; and feeds on the leaf.

Compound ash leaves start out healthy in the spring and then quickly start to curl once the nymph (immature) stage of the insect begins feeding. Once the leaves are curled, they are photosynthesizing less and may prematurely turn yellow. In the next year the tree might also have tip-kill and may only produce shoots from its trunk. Successive yearly infestations can lead to tree death as the tree’s reserves are tapped out.

Swamp Ash

In any pruning courses I teach, my main theme is to keep the trees well watered, pruned and fertilized, and they will be able to tolerate much of what Mother Nature can dish out. However, if the tree is planted in the wrong location, it may be doomed anyway. Black Ash trees are native to Eastern Manitoba, and out east they are referred to as Swamp Ash. Therefore, one can only deduce that with Calgary’s current and future drought patterns this tree would do best if it were planted in a wetter area of the yard. For Black ash trees planted in front yards prone to Chinooks or drying winds, only a minor infestation of Cottony Ash Psyllid could send the plant into shock.

Control

Since the Psyllid lays its eggs in leaf scars and bud tips to overwinter, dormant oil sprayed in early spring may be effective. Spraying Trounce (soap/permethrin mix) as the nymphs emerge in mid to late June has been found to provide even better control. The timing of this application is critical for success; just after bud break but before the leaves curl. There is a second generation of nymphs that appear in the last week of July but are tough to spray because leaves are already curled and there are lots of places for the Psyllid to hide.

More information appears in the City of Calgary/ urban forestry website.

If you have purchased and planted a tree somewhere in the Calgary area you know that the demand for quality trees is greater than the supply. The purchasing, hauling and planting costs of a reasonably sized tree can be expensive for the average homeowner (I met a customer in NW Calgary who paid $750 to have a 2-3 inch caliper willow planted in her front yard). Over the past year, I have provided tips and techniques to help you plant and maintain your trees. In this article, we will focus attention on a great insurance policy for newly planted trees: fertilizer. If used properly and judiciously, fertilizer is a great tool and insurance program for the keen gardener.

Nutrient Deficiencies in Soil

A common problem with urban soils is the lack of nutrients available to the tree. The natural leaf/ plant/ animal composting that naturally exists in the forest floor does not exist in our little ‘piece of heaven’. Also, the poor sub-surface soil structure present in Calgary’s sprawling developments hinders root growth. Trees can be perfectly planted, but once their roots hit the compacted clay, they often have a tough time unlocking nutrients.

Timing

In the spring, trees actively take up nutrients from the soil as soon as the ground thaws. For Calgary, this is usually after the May long weekend. This is often the time when many homeowners apply fertilizer to their lawn, and believe that this application will provide enough fertilizer for the trees as well. This is not the case! The turfgrass will likely take up the majority of the surface application of fertilizer, leaving little for the trees. Most of the tree’s roots are in the first meter of soil and thus, an injection of properly balanced water-soluble tree fertilizer within the tree’s drip-line as soon as the first leaves appear (e.g., late May/early June) will maximize tree growth and health.

Fertilizing in the summer (late June through August) generally is not needed as Calgary has a short growing season and in the summer root growth is at a minimum. However, if the soil condition is poor and the tree is suffering, then an application during Stampede week could prove helpful.

The Right Mix

Fertilizer mixtures contain varying levels of Nitrogen, Phosphorus and Potassium (N-P-K), three of the macronutrients that are very important for health. Nitrogen is the main nutrient the tree uses for growth and though it affects all parts of plants, it’s needed most in the development of shoots and roots. In Calgary, due to our Chinook/dry winter climates, we have to be careful not to over-apply N as this will cause excessive shoot growth that tends to get tip-killed during the winter. Also, an excess of N will encourage insects that feast on succulent shoots. The fertilizer analysis of 20-20-20 is a good, all-purpose mix for the spring. A mix containing over 20% N should contain slow-release Nitrogen or it can cause over-elongated growth. I prefer to choose mixes where the N is as low as possible, e.g., 10%, combined with equal, higher, parts of Phosphorous and Potassium. Phosphorus contributes to new shoot growth, which in turn stimulates larger root development. Potassium promotes thickening of cell walls and is therefore important in protecting plants from disease. Most professional fertilizers will also have other micronutrients, beyond the N – P – K, in their mix which add ‘extra coverage’ in the overall insurance plan.

Soil Tests

Trees require 18 essential elements for growth. How do we know exactly how many nutrients are available to our tree? A technique I have been using more frequently is to perform a soil nutrient test, done by collecting soil samples from the drip line of a specific tree and submitting the samples to a soil lab. In most cases, the Nitrogen levels are found to be low. As previously mentioned this is due to our clean yards free of leaf litter and organic matter. Also, interestingly, it’s been found that composted soil containing wood matter leaches N from the soil as it breaks down the wood particles. However, this should not stop you from using wood-chip/bark mulch as there are numerous benefits to using it around tree wells, shrubs and perennial beds. A simple extra application of Nitrogen in your mulched beds is easier than picking a thousand weeds.

Most tree companies in Calgary provide a deep-root fertilization service that is part of a comprehensive plant health care plan. If the tree is properly pruned, fertilized and watered, then it will stand the best chance of surviving most of what Mother Nature has to offer.

They say that the best time to plant a tree is 25 years ago. The next best time to plant a tree is today! Once you’ve made the decision to plant a tree, the way in which you ‘plunk’ it in the ground is crucial.

Location, Location, Location

The usefulness of Arborists would be greatly reduced if trees were planted in the proper locations. I recently said to one of my employees that I will probably be able to put my son through college with the revenue generated from removing and/or shaping ‘grade 3 trees’. You have to know the mature size of the tree before planting. For example, spruce need approximately 15 feet from their trunks to any other object such as a house, sidewalk, or power line. With today’s ‘restricted’ yard sizes, an appropriate tree type and one that is growing in popularity is the columnar variety. These often can be contained to five or six feet in diameter, making them perfect for many corners of a yard where a traditional tree is simply too expansive.

Preparing the Hole

To establish the ideal planting hole, make sure the hole is 2-3 times the width of the root ball. The depth of the hole should not be deeper than the depth of the root ball to avoid settling. In Calgary’s notoriously bad soils, the planting hole should be amended with good soil in order for root hairs from your new tree to get a good head-start.

Planting

As you are placing the tree in the hole, be careful not to rip any bark off the trunk, as even a little damage now can cause big repercussions down the road. When placing the tree in the hole, the top of the root ball cannot be lower than the final grade of the soil. Tree roots need as much air as they do water in order for them to flourish. In fact, you may want to first create a berm of good quality soil and plant a number of new trees together on the berm. It will create a pitcher’s mound effect for your planting site, and is especially appropriate for numerous trees, a big yard, or when a lot of good soil is available. When berming, be careful not to affect the intended drainage patterns in your yard.

When planting a balled and burlapped tree, cut away any excess burlap because it will act as a wick and draw moisture up from around the roots of the tree. If there is a wire basket present, it should be cut away as much as possible to avoid hindering root development.

When you are back-filling your planting soil, be sure to tamp the soil to get rid of any air pockets. When you begin back-filling, ensure that the tree is straight. If the tree is not perfectly straight, you will encounter hassles later associated with staking the tree and/or tripping over the staking wires.

Staking Trees

If you are in a very windy part of the City or if the houses around you create a wind tunnel, then staking a new tree is a good idea. Always place your first stake on the windy side of the tree. In Calgary, this is usually the Northwest. If the tree shifts due to wind after planting, then you might be breaking off the minute root hairs that are so important for growth. There are many ways to stake a tree but remember two things, don’t leave the stakes on for more than two years and use a garden hose around the staking wire to prevent girdling.

Following procedures such as these when planting is helpful to offer a new tree the best chance for survival and long-term success. However, that said, my horticultural experience has also shown me that you can ‘baby’ a tree to death or sometimes you can ‘plunk’ it in the ground and walk away and it will grow well. So, I suggest trying different methods but using common principles and common sense and you will likely grow a healthy tree. Remember…in horticulture, if you’re not killing things once in a while, you’re not learning.

For more information on tree planting and other tree related topics you can check out treesaregood.com, a website set up through the ISA (International Society of Arboriculture) main webpage. Good Luck!

In the last article we discussed planting the right tree, properly, in the right location. This article looks at post-planting care in order to protect your investment.

Watering

The most important factor in care of trees is water. Too much or too little water leads to 80% of tree-related problems that arborists encounter. One philosophy regarding watering new trees is to let the tree sit after planting for 48 hours before watering. According to this philosophy, the tips of the fine root hairs need to callous-over before being submerged in water. After the first few days a visual and/or hands-on check of the soil around the roots will tell you when calluses have developed and it’s time to water. In the following two to three weeks, make sure to keep the tree well-watered with rates dependant on your specific soil situation.

Through the spring and summer, the amount of water needed for your trees is greater than that needed for your lawn. When you are out gardening, let a hose trickle around each individual tree once every couple of weeks. Note that birch trees need five times more water than any other tree, so give them extra. Remember to water deeply and infrequently thus promoting deep root growth leading to healthier, more drought-resistant trees.

Try to harden-off your more mature trees as you approach winter. So, water them sparingly from September 15 to October 15. Then give them a good blast of water in late October or whenever you shut off your irrigation. The extra water will ensure the tree has enough moisture near the root ball to last through winter Chinooks until April. During the depths of winter, try snow-farming, which means to put extra snow over the roots of your trees and shrubs.

Pruning

There is an old myth that says you should prune a newly planted tree. People used to routinely give new trees a “haircut” at planting time. What has been found, however, is that by removing the upper parts of the tree you are sending hormonal signals to the roots to stop growing! Therefore, keep your pruner in your pocket for a couple of years in order to let the tree get a good start. If there are broken or diseased branches, however, remove them at planting time.

Fertilizing

A great way to protect your investment is to inject timely applications of fertilizer during the first years of your tree’s life. Tree fertilizer spikes are not recommended as they burn the fine root hairs where they are inserted into the soil and they do not break down uniformly. Try water-soluble fertilizer deep-root injected into the soil; this seems to be more effective in helping the tree take-up nutrients. Go easy on the amount of nitrogen you use, especially in Calgary. Due to the Calgary Chinook zone you may see a lot of tip-kill on a tree if it is given too much nitrogen over the course of the year. Aim for a recipe containing more phosphorus and potassium to invigorate young roots.

Mulching

More important than any fertilizer but not more important than water is to put a layer of mulch around your new tree. Wood-chip bark mulch is the greatest horticultural gift you can give your tree. The type of mulch that works best has good size chunks of wood in it so that it won’t break down. (Remember, though, big pieces of wood will blow away more easily in the wind!) Non-leafy mulch is best, as it will not deplete your soil of nitrogen. Here are just some of the benefits of mulch:

It holds soil moisture.

It slows weed growth.

It keeps soil temperature even throughout drastic changes in weather, particularly useful for us in Calgary.

It keeps grass from growing around your tree.

It lessens the risk of mechanical damage.

It adds organic material to your soil.

It stops the surface roots from being exposed when first watering.

At most four to five inches of mulch are needed. Any more than five to six inches will suffocate the tree. Be sure not to put mulch up against the trunk of the tree since this can lead to crown rot.

What I preach to my clients is that if you keep your new tree healthy through proper watering, pruning, fertilizing and mulching, you will be rewarded with a healthy tree. If you use these common sense ideas then you will have a stress-free tree that is resilient to most pests. (Only 5-10% of my customers use pesticides or do any spraying whatsoever in their yard). When the tree’s reserves are depleted, it’s more likely to be infested with bugs. Even in heavy snowfalls like we tend to get in May/ June, a healthy tree should be able to withstand most of what Mother Nature has in store.

For more information on tree care topics, check out treesaregood.com, a website set up through the ISA (International Society of Arboriculture) main webpage. Good Luck!

BLACK KNOT FUNGUS….IS IT DRIVING YOU “KNOTS”?

(Calgary Horticultural Society Newsletter, Dec 1, 2002)

As many Calgary gardeners know, the winter season is the best season to prune many types of trees (as long as it isn’t –20C)! One of the main reasons for performing winter pruning is that there are no diseases flying around because the trees and shrubs are dormant. When you make a pruning cut on your trees, you are creating a wound that the tree has to seal over. If you cut your trees in the winter, then the wound can slowly callus over before May/June of the next year when trees are very active. One disease that prairie gardeners should be on the lookout for is the dreaded black knot fungus.

In Calgary, black knot affects maydays and Schubert chokecherries as well as native chokecherry stands. There is a lot of black knot in the south part of Calgary where Fish Creek Park meanders through many communities. On every street you are guaranteed to find some black knot in the South. Now, we are beginning to see black knot in every area of Calgary. Before I get everyone excited and running around with chainsaws in their hands lets explain the basics…

Life Cycle

Black knot is caused by the fungus Dibotryon morbosum. The disease cycle starts with spores that usually infect the tips and twigs of the branches. These spores have been carried over in wind and rain from other galls on the same tree or in trees within close proximity. The first symptoms are light swellings on the branches. Then the swellings turn brownish, grow larger in the infected area, turn black and form a gall. The gall most often girdles the complete branch it is infecting, and then kills the branch.

Controls

Pruning is the only effective way to control this disease. Fungicides would have to be applied too often throughout the growing season to be effective. If you are brave enough to cut your own trees and you have taken a course or have been trained by a Certified Arborist, then make a pruning cut at least 8 inches below the point of infection. Do not leave your prunings lying around either, burn or bury them.

As soon as you see the swelling start to occur, at any time of year, prune out that growth! A major problem exists when the black knot is infecting the trunk of the tree and thus pruning below the point of infection means taking out the whole tree. If you catch the disease forming in the trunk of the tree then carve out the infection with a sharp knife. If the level of infection in the tree is too severe, then you will have to look at removing and replacing the tree. It pains me to see an old tree taken down because it is too infected, so make sure you catch the disease early.

Robin Adair is a Certified Arborist and owner of Arbour Crest.

KEEP BLACK KNOT OFF YOUR TREES!

(Article for Park Patter newsletter, April 27, 2002)

Have you noticed black, unsightly growths on your trees or those of your neighbors?

As a concerned tree care specialist, I would like to let you know about an invasive tree disease called Black Knot.

Black Knot is a fungal disease that spreads through the air in the cherry family. Locally, the trees that are affected are Mayday, Schubert Chokecherry, and native Chokecherry. There is a lot of Black Knot on the trees in the further south part of Calgary because the native plants in Fish Creek Park act as hosts and go unpruned. The situation is not so bad in Springbank – yet! If we are diligent, we should be able to keep Black Knot from invading our “piece of foothills heaven”.

In the first year of Black Knot infection, the branch becomes slightly swollen and the disease is barely noticeable. In the second year, you’ll notice what looks like black growths appearing on the branches. These are especially visible in the winter when there are no leaves to hide the infection. The knots continue to grow until the branch becomes girdled and dies. If the fungus is present in the stem of a tree, the tree will eventually have to be removed, as the infection cannot be pruned out. If the knot only forms on the branches, then you can prune out the infected branches and hope it does not reappear.

To control this disease, it must be pruned out and the infected branches burned, bagged, or buried. Have a professional arborist prune the tree every 2-3 years to keep the tree healthy and monitor infection. This will help reduce the risk of spreading to your neighbor’s trees as well! Applications of fungicide can also be used as a preventative measure, combined with pruning. However, multiple applications of fungicide would be required throughout the growing season, making this option somewhat impractical and potentially harmful.

If you’re already knowledgeable about proper pruning practices and you want to prune out Black Knot, make your pruning cuts one foot below the point of infection to ensure that you get at any contamination that has gone into the stem. Prune when the trees are in a dormant mode so that you are not creating wounds unnecessarily during the growing season. If you are not sure how to make proper cuts, contact an arborist for assistance.

WINTER PRUNING

(Article for Calgary Horticultural Society, Feb/Mar 2002 issue)

By: Robin Adair

As the winter season drags on, we Calgary gardeners are anxious to see the arrival of spring when we can tinker in our backyards. One great feature about Calgary is that the weather generally stays warm enough to prune year-round. The phone rings off the hook for the tree companies in the spring and summer, but most arborists will agree that winter is often a better time to prune for the health of the trees. The keen gardener can do many things around the house and yard to prepare for warmer days, but nothing has such a visual impact in your yard as pruning. The following are things to keep in mind when winter pruning.

Tree Pruning

The starting point to any pruning job is to make sure you have properly identified your trees and shrubs. This point cannot be stressed enough in that there is a plethora of timing concerns that vary from tree to tree. For example, you would not want to make too many cuts on Birches or Maples until they are in full leaf. If you cut ‘bleeders’ when they are dormant, they will lose water from those cuts next spring, causing a loss in water pressure leading to tree stress.

Except for Birches and Maples, winter is a great time to prune deciduous trees. During the winter:

There are no diseases or insects floating around looking for a host,

There is good access to the tree visually and structurally,

There are no leaves to haul away, and

Winter pruning stimulates growth, as nutrients stored in the roots need a place to go in spring.

Winter is also the best and only time to prune Elms – the City bylaws state that you can only prune Elms from October 1 to April 1. This ensures that pruning is done while no Elm Bark Beetles carrying the Dutch Elm Disease fungus are flying around. The beetle is present in Calgary, but not the disease…yet!

Removals

Even if your neighbour received a brand-new chainsaw for Christmas; don’t let them cut down your Poplars, Willows or Maydays in winter because suckering might be a problem come spring. However, if you are planning on removing your Spruce or Pine, then any time of year is fine, as conifers do not sucker. Perhaps, save the conifer removal until next fall when you can take it down and use it as a Christmas tree. Make sure to remove all squirrels before bringing these trees into the house!

Shrub Pruning

If you have any old shrubs that are not performing well, i.e., have a lot of deadwood and disease, and you don’t have the patience to make a lot of cuts, then cut them flush to the ground. Do not leave stubs at the base as this will look unsightly and the stubs will rub up against next year’s new shoot growth. Shrub flushing is a great rejuvenation technique, and very effective at scaring your significant other into thinking you are a tree butcher. Most shrubs can handle flushing if in good health – but check with an Arborist if unsure.

Safety

As with any pruning, safety should be foremost in your mind. From using ladders in tall trees to the use of sharp tools when doing shrub pruning, or God- forbid using chainsaws, common sense and the proper safety equipment is critical.

Hopefully these tidbits will get you into the pruning mood. However, the type of cuts you should be making and the placement of these cuts within the tree is even more important. Prior to making those first cuts, take a course to learn proper techniques. Or, if the job and the thought of the clean-up is too ominous, then call your favourite arborist.

If you would like to discuss this article in further detail please e-mail me at robin.adair@sasktel.net. Happy pruning!